A NEW IN-VIVO TECHNIQUE FOR 3-DIMENSIONAL SHOULDER KINEMATICS ANALYSIS

Objective. The field of shoulder kinematics research has long relied u pon the use of cadaveric models or invasive techniques in human volunt eers. In this paper, a novel method is presented that utilizes magneti c resonance imaging (MRI) and a software system called 3DVEWNIX, This method permits non-invasive, repetitive evaluation of living patients for glenohumeral kinematics analysis, The objectives of this study wer e twofold: to validate the quantitative accuracy of this technique; an d to demonstrate glenohumeral relationships in asymptomatic volunteers during internal and external rotation of the arm, Design, The transla tional accuracy was first assessed by comparing known cadaveric glenoh umeral translations with calculations from MR images of the cadaver. N ine asymptomatic volunteers were subsequently placed in an external sh oulder positioning device in the scanner and imaged in 10 degrees incr ements of actively achieved internal and external rotation, Three-dime nsional reconstructions of the glenoid and humerus were used to evalua te the glenohumeral relationships in the tested positions of rotation. Results. The quantitative analysis revealed an error of 0.61 mm (SEM 0.11 mm), Examination of the volunteers demonstrated normal relationsh ips about the glenohumeral joint in internal and external rotation. In addition, this method provided detailed images of the bony surface ar chitecture from any perspective. These images can be transformed into a cinematic three-dimensional depiction of active shoulder rotation. C onclusion, This new technique offers an accurate, non-invasive method for assessing the normal glenohumeral relationships in shoulder kinema tics, We now possess the capability to investigate the kinematics of n ormal and abnormal shoulder conditions non-invasively in a large patie nt population.